Method for Switching a Terminal Over from a First Radiocommunications Network to a Second Radiocommunications Network, Corresponding Computer Program Product, Storage Means and Terminal

1. A method for switching a radiocommunications terminal from a first radiocommunications network, with which the terminal is synchronized and registered, to a second radiocommunications network, the terminal having first and second connection profiles associated respectively with the first and second radiocommunications networks, wherein said terminal performs the following steps: for said second connection profile, preliminary and at least partial synchronization of the terminal with the second radiocommunications network; receiving a request for making an outgoing call by the terminal on the second radiocommunications network; and in response to the request for making the outgoing call, the terminal performs the following acts: complete synchronization, based on said preliminary and at least partial synchronization, of the terminal with the second radiocommunications network; and registration of the terminal with the second radiocommunications network.

2. The method according to claim 1 , wherein the step of preliminary and at least partial synchronization comprises a step of frequency scanning in a predetermined frequency band and of measuring reception power level of beacon frequencies of the second radiocommunications network.

3. The method according to claim 1 , wherein the step of preliminary and at least partial synchronization comprises the following steps: frequency scanning in a predetermined frequency band and measuring reception power level of beacon frequencies of the second radiocommunications network; and time and frequency synchronization of the terminal with the beacon frequencies of the second radiocommunications network.

4. The method according to claim 1 , wherein the step of preliminary and at least partial synchronization is reiterated.

5. The method according to claim 4 , wherein the step of preliminary and at least partial synchronization is reiterated in one of the following ways: periodically; upon positive verification of one of the following events: detection of a change in position of the terminal; detection of a request for reiteration of preliminary and at least partial synchronization via a man/machine interface.

6. The method according to claim 1 , comprising the following steps, the second connection profile being stored on at least one detachable card inserted in the terminal: extracting said second connection profile from said detachable card; storing said extracted second connection profile in a local storage memory included in the terminal of said extracted connection profile.

7. The method according to claim 6 , wherein the results of said preliminary and at least partial step of synchronization of the terminal are stored in the local storage memory.

8. The method according to claim 1 , wherein: the second network belongs to a plurality of second radio communications networks, the terminal has a second connection profile for each of the second radiocommunications networks, the terminal performs said preliminary and at least partial synchronization step for each of the second connection profiles.

9. A non-transitory computer-readable storage medium storing a computer program product comprising program code instructions for implementing, when said program is executed on a computer, a method for switching a radiocommunications terminal from a first radiocommunications network, with which the terminal is synchronized and registered, to a second radiocommunications network, the terminal having first and second connection profiles associated respectively with the first and second radiocommunications networks, wherein said instructions configure the terminal to perform the following steps: for said second connection profile, preliminary and at least partial synchronization of the terminal with the second radiocommunications network; receiving a request for making an outgoing call by the terminal on the second radiocommunications network; in response to the request for making the outgoing call, the terminal performs the following acts: complete synchronization, based on said preliminary and at least partial synchronization, of the terminal with the second radiocommunications network; and registration of the terminal with the second radiocommunications network.

10. A radiocommunications terminal configured to switch from a first radiocommunications network, with which the terminal is synchronized and registered, to a second radiocommunications network, the terminal having available first and second connection profiles respectively associated with the first and second radiocommunications networks, wherein the terminal comprises: means for preliminary and at least partial synchronization of the terminal with the second radiocommunications network, activated for said connection profile; means for receiving a request for making an outgoing call by the terminal on the second radiocommunications network; means for complete synchronization, based on said preliminary and at least partial synchronization of the terminal with the second radiocommunications network; and means for registering the terminal with the second radiocommunications network; said means for complete synchronization and registration of the terminal being activated upon the terminal receiving the request for making the outgoing call.

11. A radiocommunications terminal configured to switch from a first radiocommunications network, with which the terminal is synchronized and registered, to a second radiocommunications network, the terminal having available first and second connection profiles respectively associated with the first and second radiocommunications networks, wherein the terminal comprises: a reprogrammable computation machine or a dedicated computation machine configured to: preliminarily and at least partially synchronize the terminal with the second radiocommunications network, activated for said connection profile; receive a request for making an outgoing call by the terminal on the second radiocommunications network; completely synchronize, based on said preliminary and at least partial synchronization, the terminal with the second radiocommunications network; and register the terminal with the second radiocommunications network; wherein the complete synchronization and registration of the terminal are activated upon the terminal receiving the request for making the outgoing call.